Boris Johnson is being urged to push for a compulsory Minimum London Wage by law because more firms are flouting the voluntary Living Wage first launched in the East End a decade ago.

A new legal minimum would cover London’s higher cost of living for rents and fares without threatening jobs or commercial competition, the London Assembly says.

Assembly Members are backing the findings of the Centre for London think tank that the minimum wage could eventually be raised by a fifth.

The Assembly’s Fiona Twycross, who proposed the move, said: “A ‘London Minimum’ would help families struggling with the spiralling cost of transport and accommodation.

“Thousands are subsisting on a wage lower than they need to look after themselves.”

The National Minimum could be raised by seven per cent and later 20 per cent in London without threatening jobs, she believes.

Campaigners from Telco, The East London Communities Organisation, called for a minimum wage in 2003 and went on to win their first success at Canary Wharf for cleaners and other low-pay workers. Tower Hamlets council and Queen Mary’s college followed, before a national minimum was introduced.

But London’s rocketing costs make it a special case, say Assembly members. Average wages fell by almost five per cent in 2012. Jobs paying less than the Living Wage have risen by 180,000 since 2007.

The Assembly wants the Mayor’s backing for a London Minimum and to “give attention to those struggling because of the cost of living crisis.”